Influence of thrombolysis on signal-averaged electrocardiogram and late arrhythmic events after acute myocardial infarction

The influence of intravenous thrombolysis on both prevalence of ventricular late potentials and incidence of late arrhythmic events was evaluated in 174 consecutive patients surviving a first acute myocardial infarction; 106 patients (61%) received thrombolysis (group A) and 68 (34%) had conventional therapy (group B). In group A, 18 patients (17%) had late potentials compared with 23 (34%) in group B (p < 0.05); mean left ventricular ejection fraction was not different (0.50 ± 0.09 vs 0.50 ± 0.10; p = not significant [NS]). Of 63 patients who underwent coronary arteriography because of postinfarction ischemia, 28 (44%) had a closed infarct-related artery; of these, 11 (39%) had late potentials compared with 3 of 35 (9%) with a patent artery (p < 0.01). Mean left ventricular ejection fraction was not significantly different between the 2 groups (0.49 ± 0.09 vs 0.53 ±0.09; p = NS). At a mean follow-up of 14 ± 8 months, 8 of 161 patients (5%) had a late arrhythmic event; 6 of 8 (75%) with and 28 of 153 (18%) without events had late potentials (p < 0.001). In group A, 4 of 99 patients (4%) had events compared with 4 of 62 (6%) in group B (p = NS, relative risk 1.6). Of 24 patients with anterior wall AMI and left ventricular dyskinesia, 6 events occurred. In this group of patients, a higher rate of events was observed (25%); 3 of 16 (19%) treated with thrombolysis had an event compared with 3 of 8 (37%) treated conventionally (p = NS, relative risk 2.6). Thrombolysis and patency of the infarctrelated artery significantly reduce the rate of late potentials independently of global left ventricular function. Although no significant difference was found in the follow-up results, the reduced rate of late potentials suggests an improved ventricular electrical stability both in patients treated with thrombolysis and in those with a patent vessel.